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<body>
    居住在海南：
    <input type="radio" id="province" name="province" value="1" οnclick="check()" checked="checked" >是
    <input type="radio" id="province" name="province" value="0" οnclick="check()" >否
    <br>
    城市：
    <input type="radio" id="city" name="city" value="1" οnclick="doCheckedCity()" checked="checked" >海口
    <input type="radio" id="city" name="city" value="2" οnclick="doCheckedCity()" >上海
    <input type="radio" id="city" name="city" value="3" οnclick="doCheckedCity()" >北京
    <input type="radio" id="city" name="city" value="4" οnclick="doCheckedCity()" >武汉

</body>

<script>
// 功能：居住在海南选"是"，城市选"海口"，选否，则不选城市
       function check(){
                 var province = document.getElementsByName("province");//省份
                 var a;
                 var provinceValue;
                 for(a=0; a<province.length; a++){//遍历单选框
                          if(province[a].checked){
                                provinceValue = province[a].value;
                          }
           }
                 var city = document.getElementsByName("city");//城市
                 var i;
                 if(provinceValue==1){
                          for(i=0; i<city.length; i++){//遍历单选框
                                   if(city[i].value==1){
                                             city[i].checked = "checked";
                                   }
                          }
                 }else{
                          for(i=0; i<city.length; i++){//遍历单选框
                                   if(city[i].checked){
                                             city[i].checked = "";
                                   }
                          }
                 }
       }
    //功能：居住在海南选"是"，城市选择除海口之外的城市都会弹出提示并选择海口
  function doCheckedCity(){
                 var province = document.getElementsByName("province");//省份
                 var a;
                 var provinceValue;
                 for(a=0; a<province.length; a++){//遍历单选框
                         if(province[a].checked){
                                 provinceValue = province[a].value;
                          }
           }
                 var city = document.getElementsByName("city");//城市
                 var i;
                 if(provinceValue==1){
                          for(i=0; i<city.length; i++){//遍历单选框
                                   if(city[i].checked && city[i].value!=1){
                                             city[i].checked = "";
                                             alert("居住在海南选择'是'，则城市只能选择海口");
                                   }
                          }
                          for(i=0; i<city.length; i++){//遍历单选框

                                   if(city[i].value==1){
                                             city[i].checked = "checked";
                                   }
                          }
                 }else{
                          for(i=0; i<city.length; i++){//遍历单选框
                                   if(city[i].checked && city[i].value==1){
                                             city[i].checked = "";
                                             alert("居住在海南选择'否'，则城市不能选择海口");
                                   }
                          }       
                 }
       }
</script>

</html>